Research On Comprehensive Analysis And Construction Method Of Urban Ventilation Channel

With the deepening of reform and opening up and the steady economic development, the process of urbanization in China has been accelerating, as of 2015, China’s urbanization level has reached 56.1%. The development of urbanization will absorb large population, expand urban construction area, but often ignore the ventilation performance of the city. The heat and high concentrations of pollutants generated by human production and life are not timely diffusion and dilution, so as to affect the comfort of urban thermal environment and wind environment. Therefore, the research of urban ventilation channel is the demand of mitigating the urban heat island effect and making urban human settlements development sustainable. On the basis of analyzing the current situation of urban wind environment from domestic and foreign research, this paper summarizes the theoretical basis of urban ventilation channel construction and puts forward the construction method combined with qualitative and quantitative analysis. Taking Hangzhou main city as an example, the above method is applied to analyze the potential urban ventilation channel, and the corresponding control measures are put forward. It provides some reference for the urban heat island effect mitigation, urban energy conservation and urban wind environment improvement, and provides scientific basis and technical guidance for the environmental improvement of public’s production, life, rest and so on.First, this paper reviews the theoretical basis of the construction of urban ventilation channel. On the basis of explicating the definition of urban ventilation channel, the author analyzes the characteristics of different type of urban ventilation channel (river type, green type and road type), and describes the key components of the urban ventilation channel, including the effect area, compensation area and urban ventilation path.Secondly, on the basis of summarizing the traditional construction methods of urban ventilation channel, this paper proposes a new constructing method based on the combining of quantitative research and qualitative analysis. To be specific, the author proposes the use of the software Erdas to analyze urban land-surface temperature inversion, then by combining the results of urban land-surface temperature with urban landscape features, green space system and urban construction to identify the effect area and compensation area. The urban ventilation paths are identified by comprehensive influence factor chart, which formed by the factors that affecting the potential of the city’s air circulation, the formation process need to use ArcGIS software for rating assignment and overlay analysis. The characteristics of the urban dominant wind directions are induced by wind rose plots, which are drawn by the statistics from a number of automatic weather stations. Finally, we constructed the urban ventilation channel by comprehensive analyzing the effect area, compensation area, urban ventilation path and the urban dominant wind directions. Meanwhile, some construction methods are proposed from different angles, including the overall urban layout, the road system, the open space system and the construction of generalized ventilation channel.Finally, the paper analyzes the potential urban ventilation channel of Hangzhou main area by the construction method which is put forward above. The surface temperature of Hangzhou main area are inversely derived by remote sensing image of May 22,2015. By the analysis results of land surface temperature of Hangzhou city, we can know that the compensation area are headed by West Lake scenic area, Qian Tang river and the Beijing-Hangzhou Grand Canal, the effect area are headed by industrial parks and large transport hubs. Selecting height of building, building density, green space, urban water system and urban road network, then according to the extent of its impact on urban air circulation potential, we can make a graded assignment and make use of GIS overlay analysis to form a chart of comprehensive influence factor, which can identify the urban ventilation path of Hangzhou. The wind roses are drawn by the date from 15 automatic weather stations. The characteristics of dominant wind direction in summer and winter of Hangzhou are analyzed by the wind roses. On the basis of all the above comprehensive analysis, we can identify six potential primary urban ventilation channel and five potential secondary urban ventilation channel. In order to realize guiding significance of the urban ventilation channels, some specific control measures for primary urban ventilation channels are put forward.